The field of the invention is that of pressure sensors using piezoelements, and the invention relates more particularly to pressure sensors adapted for use in the wall of a pressure zone housing or the like.
A sensor is known for measuring the pressure of a medium, in particular for measuring the changing pressure in a diesel injection pump, comprising a screw bolt with an axial bore extending through the entire head and shank of the bolt, a transducer placed inside said bore which can convert a pressure change into an electrical signal, an electric cable leading via the bolt head to the transducer, and a non-compressible mass which is provided in the bore and extends from the pressure measurement side of the bolt up to the transducer.
Such a sensor is known from international patent application WO-83/00225. See also the commonly assigned, copending U.S. patent application Ser. No. 07/485,117, filed Feb. 23, 1990.
Screwing such a sensor at the position of a vent screw through an opening in the wall of a diesel injection pump means that when the diesel engine is turning this sensor can provide data on the injection moment, the wear on the pump, the opening pressure of the injector and the wear on the injector.
In the case of the known sensor the transducer has the pressure-sensitive element placed in a Wheatstone bridge circuit. The fitting of the Wheatstone bridge in the bolt bore is difficult to incorporate in an easy and automated production method.